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In this paper, a process of pre-oxidation and magnetization roasting followed by low-intensity magnetic separation and acid leaching (OMLA) was developed to separate and recover iron from siderite ore with high-magnesium and high-manganese. The pre-oxidation of siderite ore was performed in a tube furnace at 800 °C for 45 min, improving the iron recovery by 6%. The effects of conditions of magnetization roasting, magnetic separation and acid leaching on the separation indices were studied. Under the optimum parameters, the iron concentrate, assaying 62.01% Fe, 8.74% MgO, 2.41% MnO with comprehensive recovery of 96.9%, were obtained through the OMLA process. Phase and microstructure transformation of the samples in OMLA process were investigated by SEM-EDS. The results indicated that pre-oxidation of siderite ore can cause porous structure of raw sample, improving reduction efficiency in magnetization roasting process. Most of gangue minerals (dolomite, ankerite, quartz and muscovite) could be removed in the process while Mn and part of Mg which existed in the iron oxides in the form of isomorphous substitution throughout the OMLA process would remain in the final concentrate.

In this study, copper slag and low-grade nickel laterite were synergistically utilized via an innovative sintering process with multi-force fields. Their sintering performance and the reduction and softening dripping characteristics of Fe–Ni–Cu product sinter were determined. The strengthening mechanism of the innovative sintering technology was revealed. The obtained Fe–Ni–Cu alloy and smelting slag from the melting dripping process were characterized. Carbon emissions reduction and other valuable elements treatment were also discussed. Due to the formation of the denser sinter microstructure and the reduction of high smelting components, sintering performances in the innovative sintering process are substantially improved. Compared with the base case, tumble index and productivity are improved by 24.87% and 19.59%, respectively. Solid fuel consumption is reduced by 27.14%. The reduction and softening dripping characteristics of Fe–Ni–Cu product sinter are excellent as well. The obtained Fe–Ni–Cu alloy with high purity can be used as the high-quality burden for copper-bearing stainless steel and high-strength alloy steel and its quality can be further improved by optimizing the smelting process parameters in the near future. In addition, the obvious carbon emissions reduction in sintering-blast furnace production can be achieved and other valuable elements such as S, Zn and Pb can be conveniently recycled in form of sulphuric acid and Pb–Zn dust, respectively.

Byline: Gu Zhengqi, Fang Gang, Wu Jun, W. Seemann Mathematical model and computer aided simulation techniques have been used to predict and analyse the steering stability of high-speed vehicles. A new vehicle dynamics simulation model, based on considering the roll motion of suspensory mass of the vehicle and the effect of side winds, has been established in this paper. The model is able to simulate the transient state of a vehicle under side winds and to analyse the steering stability and veering character of the vehicle. Some simulation results are presented and discussed.

At present, deep learning is a hot topic in the field of the classification of hyperspectral image (HSI), and it has aroused wide attention. However, in fine-grained classification tasks, such as tree species classification, the uncertain spectrum remains the major factor restraining the classification performance. In order to solve the dilemma of forest tree species classification, a dual-concentrated network with morphological features (DNMF) is proposed. First, mathematical morphology is used to extract the morphological features of HSI. Then, coarse-grained information is extracted from the original hyperspectral data, and fine-grained information is extracted from morphological features. After that, both morphological representations and spectral inputs are fed into DNMF, and the overall evaluation index and visual image are obtained. The advantage of DNMF is that it decouples the spatial and spectral information, and a multisource information fusion process is then simulated. Accordingly, DNMF obtains high tree species classification accuracy. In order to verify the superiority of DNMF, we choose Gaofeng State-owned Forest Farm in Guangxi Province and the Belgium dataset, which was collected near the western part of Belgium as the research area. Related experiments demonstrate that the DNMF model achieves clearly better classification performance over other competitive baselines.

Iron ores always contain several forms of alumina, which may have different effect on sintering performance. In this paper, sinter pot tests were systematically conducted with various alumina types and contents by means of alumina additives substituting for the corresponding types of alumina, and the relevant action mechanism on sintering performance was clarified by the mineralogy of product sinter. The results show that kaolinite is beneficial to the granulation process rather than other three alumina types. In addition, it contributes to relatively better sintering performance while aluminous goethite ranks the only next, followed by gibbsite and free alumina. Mechanism analysis indicates that kaolinite and aluminous goethite are preferable to achieve relatively lower sinter porosity and higher amount of silico-ferrite of calcium and alumina (SFCA) compared with gibbsite and free alumina. Besides, the former two alumina types are apt to promote the formation of higher strength SFCA such as dendritic and acicular SFCA. Furthermore, much tighter interlocking texture in product sinter is formed as alumina occurs in kaolinite or aluminous goethite. Kaolinite and aluminous goethite are the preferably desirable alumina types for sintering rather than free alumina and gibbsite.

This study is aimed to obtain better-quality Ni–Cr composite sinter for the production of 300 series stainless steel via the sintering-blast furnace process at lower cost. Based on the complementary advantages of limonitic nickel laterite and chromite, co-sintering pot tests of the two ores were conducted in various chromite proportions and then strengthened by multi-force fields. Mechanistic analysis was performed, including the chemistry and mineralogy of product sinter and the thermodynamic and kinetic conditions of the co-sintering process. The results indicate that the addition of chromite effectively improves tumble index and productivity, especially at a chromite ratio of 15%, due to the improvement of sinter microstructure and the thermodynamic and kinetic conditions during sintering. However, solid fuel rate is increased gradually because of the greater amount of high smelting minerals. With the application of multi-force fields, higher tumble index is obtained owing to the further densification of sinter bed and the formation of tighter interlocking texture. Solid fuel rate is greatly decreased due to the efficient supply of extra physical heat. Productivity is weakened to some extent as the flame fronts speed is reduced. In addition, excellent metallurgical performance is achieved. The co-sintering process of limonitic nickel laterite and chromite is significantly improved via multi-force fields.

Recovery of valuable metals from red mud smelting separation slag is important for environmental protection and saving of natural resources. In this paper, we propose a recycling process of red mud smelting separation slag by mineral phase reconstruction conducted under an air atmosphere. In this process, NaOH and Ca(OH)2 roasting of Al2O3 and NaAlSiO4 was performed, and Al2O3 and SiO2 were converted into alkaline-soluble NaAlO2 and Ca2SiO4, respectively. In the consequent steps, more than 80% of Al2O3 was selectively dissolved into a leaching solution using a NaOH solution under 95 °C, and the obtained NaAlO2 solution can be used as a source for extracting alumina. Then, a 20 wt.% HCl solution was used to remove SiO2 from the residue, obtaining a SiO2-containing solution and a concentrated residue of undissolved TiO2 and CaO. Finally, this mineral phase reconstruction process can enable a higher metal leaching rate, and this study provides a novel, clean, and sustainable method for recycling valuable metals from red mud smelting separation slag.

The alumina content of iron ores for sintering is gradually increasing with the growing depletion of high-grade iron ores, which is harmful to the sintering process. Therefore, it is essential to reveal the action mechanism of alumina on sinter quality. In this paper, the aluminum occurrence of various iron ores was determined by applying X-ray diffraction (XRD), optical microscopy, scanning electron microscopy and energy dispersive spectrum analysis (SEM-EDS). Then, the effects of iron ore type, aluminum occurrence (free alumina, gibbsite, diaspore, alumogoethite and kaolinite) and alumina content on formation characteristics of SFCA bonding phases as well as sinter matrix strength were investigated based on laboratory compact sintering tests. The results show that the discrepancy of aluminum occurrence contributes to different SFCA formation characteristics and then sinter matrix strength, due to different reactivity of various aluminum-containing minerals with iron oxides and fluxes. Increasing alumina content generally results in an increase in the porosity of sinters and deterioration of sinter matrix strength for all aluminum occurrence. Aluminum in the form of kaolinite is more conducive to form dendritic or acicular SFCA with superior sinter matrix strength compared with other aluminum occurrences. In contrast, aluminum occurring in free alumina presents greatest adverse impacts on sinter matrix strength due to its poor reactivity and high porosity of resultant sinters.

Direct reduction-magnetic separation process (DRMSP) is a highly effective and clean method to upgrade the complex resources, which has been widely used to recovery the value metals in copper slag (CS) and nickel laterite (NL) in recent years. Adequate growth of the alloy particles is a key parameter influencing the complete extraction of alloys from CS and NL in this process. Therefore, the liquid phase formation mechanism, growth kinetics of the alloy particles, and the correlation between the alloy particle growth and liquid phase formation were studied to reveal the synergistic effect of the co-reduction of CS and NL. The results indicated that fayalite in the copper slag reacted with forsterite in nickel laterite to form augite group minerals with low melting points, resulting in more liquid phase formation in the reductive roasting process. A comparison with the reduction kinetic parameters of the single nickel laterite showed that the growth index and activation energy decreased significantly from 2.85 and 272.98 KJ/mol to 2.08 and 171.99 KJ/mol, respectively, after the addition of 40% copper slag, which confirmed that copper slag promoted the particle growth. Moreover, the liquid phase increased the total cohesive force between the alloy particles, revealing the correlation between alloy particle growth and liquid phase.

As is well known, the process of direct reduction and magnetic separation is effective route to deal with low-grade saprolite laterite, but generally limited by the reduction of nickel (iron)-bearing minerals and growth of Fe-Ni alloy particles in the reduction process, causing the low recovery of nickel and iron. To improve beneficiation of nickel and iron from low-grade saprolite laterite with 1.29 wt.%Ni and 16.31 wt.%Fe, co-reduction with limonitic laterite ore and basicity optimization were adopted as strengthening measures in this paper with better economic efficiency than before. The enhancing mechanism was investigated via the thermodynamics analysis and mineralogical study. The phase transformation and growth behaviors of metallic alloy particles during reduction process were revealed as well. The results indicated that co-reduction with limonitic laterite ore is capable of promoting phase transformation from Ni2SiO4 in saprolite laterite to NiFe2O4. CaCO3 can not only destroy the structure of magnesium silicate to release nickel(iron)-bearing phase, but also enhance the reduction of Fe2SiO4 to form efficiently iron-based eutectoid with nickel and liquid phases to accelerate the growth of Fe-Ni fine particles larger than 40 μm. A superior crude alloy was obtained with 5.11 wt.%Ni and 82.15 wt.%Fe with corresponding recovery rates of 91.89% and 85.15% respectively. Keywords: Nickel laterite ore, Co-reduction, Basicity, Phase transformation, Particle growth, Fe-Ni alloy

The forest tree height and aboveground biomass (AGB) are important indicators for monitoring changes and trends in forest carbon storage and terrestrial carbon fluxes. Accurate large-scale wall-to-wall mapping of the forest tree height and AGB remain challenging due to the limited data availability for extraction tree height and the data signal saturation problem in AGB estimation. In this study, we explored the potential of forest tree height mapping using stereo imageries, and analyzed whether accounting for such information, in addition to optical sensor data, could improve the performance of AGB estimations of coniferous forests in a case study in North China. First, a spatially continuous tree height product was obtained using Ziyuan-3 satellite (ZY-3) stereo images combined with a digital elevation model (DEM) obtained from Advanced Land Observing Satellite (ALOS) data. Second, two AGB estimation models were established by combining the forest tree height with vegetation index, spectral, biophysical (from Sentinel-2 images), and topographic variables. A random forest algorithm was utilized to evaluate the effect of including the tree height variable in the AGB estimation. The results showed that the tree height estimation using the nadir and forward views of the ZY-3 stereo images was more accurate than that based on the nadir and backward views from the same images. The AGB estimation model incorporating the tree height variable with a coefficient of determination value of 0.7789, a root mean square error (RMSE) value of 29.815 Mg/ha and a relative RMSE of 23.42% was more robust and effective, thereby demonstrating that the tree height variable can be used to alleviate the data signal saturation issue successfully. The proposed approach can provide new insight into forest tree height mapping and AGB products obtained from satellite stereo images and freely accessible Sentinel-2 multispectral images.

In this paper, an innovative method is proposed to upgrade iron and remove phosphorus from high-phosphorus oolitic hematite ore by the sodium magnetization roasting–magnetic separation–sulfuric acid and sodium hydroxide leaching process. The process parameters of sodium magnetization roasting, acid leaching, and alkaline leaching were optimized. The results show that by only adopting traditional magnetization roasting–magnetic separation, an iron ore concentrate containing 57.49% Fe and 1.4% P2O5 at an iron recovery rate of 87.5% and a dephosphorization rate of 34.27% was produced, indicating that it is difficult to effectively dephosphorize and upgrade iron by the conventional magnetization roasting–magnetic separation process. The obtained rough magnetic concentrates were then subjected to acid and alkaline leaching steps, and the final product, assayed at 64.11% iron and 0.097% P2O5, was manufactured successfully. Moreover, the added NaOH could promote the mineral phase reconstruction of aluminum- and silica-bearing minerals during magnetization roasting and intensify the upgrading of iron as well as enhance the growth of iron grains.

An efficient and accurate forest sample plot survey is of great significance to understand the current status of forest resources at the stand or regional scale and the basis of scientific forest management. Close-range photogrammetry (CRP) technology can easily and quickly collect sequence images with high overlapping to reconstruct the 3D model of forest scenes and extract the individual tree parameters automatically and, therefore, can greatly improve the efficiency of forest investigation and has great application potential in forestry visualization management. However, it has some issues in practical forestry applications. First, the imaging quality is affected by the illumination in the forest, resulting in difficulty in feature matching and low accuracy of parameter extraction. Second, the efficiency of 3D forest model reconstruction is limited under complex understory vegetation or the topographic situation in the forest. In addition, the density of point clouds by dense matching directly affects the accuracy of individual tree parameter extraction. This research collected the sequence images of sample plots of four tree species by smartphones in Gaofeng Forest Farm in Guangxi and Wangyedian Forest Farm in Mongolia to analyze the effects of image enhancement, feature detection and dense point cloud algorithms on the efficiency of 3D forest reconstruction and accuracy of individual tree parameter extraction, then proposed a strategy of 3D reconstruction and parameter extraction suitable for different forest scenes. First, we compared the image enhancement effects of median–Gaussian (MG) filtering, single-scale retinex (SSR) and multi-scale retinex (MSR) filtering algorithms. Then, an improved algorithm combining Harris corner detection with speeded-up robust features (SURF) feature detection (Harris+SURF) is proposed, and the feature matching effect is compared with that of a scale invariant feature transform (SIFT) operator. Third, according to the morphological characteristics of the trees in the sequence images, we used the iterative interpolation algorithm of a planar triangulation network based on geometric constraints (GC-based IIPTN) to increase the density of point clouds and reconstruct the 3D forest model, and then extract the position and DBH of the individual trees. The results show that MSR image enhancement can significantly increase the number of matched point pairs. The improved Harris+SURF method can reduce the reconstruction time of the 3D forest model, and the GC-based IIPTN algorithm can improve the accuracy of individual tree parameter extraction. The extracted position of the individual tree is the same as the measured position with the bias within 0.2 m. The accuracy of extracted DBH of Eucalyptus grandis, Taxus chinensis, Larix gmelinii and Pinus tabuliformis is 94%, 95%, 96% and 90%, respectively, which proves that the proposed 3D model reconstruction method based on image enhancement has great potential for tree position and DBH extraction, and also provides effective support for forest resource investigation and visualization management in the future.

Waste copper slag is a typical hazardous solid waste containing a variety of valuable elements and has not been effectively disposed of so far. In this paper, a stepwise extraction process was proposed to recover valuable elements (copper, iron, lead and zinc) from waste copper slag. The specific procedures are as follows: (1) A flotation process was adopted to enrich copper, and when the copper grade in the flotation concentrate was 21.50%, the copper recovery rate was 77.78%. (2) The flotation tailings were pelletized with limestone, then the green pellets were reduced, and the magnetic separation process was carried out. When the iron and copper grades in the magnetic concentrate were 90.21% Fe and 0.4% Cu, 91.34% iron and 83.41% copper were recovered, respectively. (3) Non-magnetic tailings were mixed with clinker and standard sand to produce common Portland cement. Several products were obtained from the waste copper slag through the proposed process: flotation concentrate, measured 21.50% Cu; magnetic concentrate, containing 90.21% TFe and 0.4% Cu; direct reduction dust, including 65.17% ZnO and 2.66% PbO; common Portland cement for building construction. The comprehensive utilization method for waste copper slag achieved zero tailing and has great potential for practical application.

Aiming at the effective utilization of the abundant high-alumina iron ores with low iron grade, the influence of alumina concentration and type on high-temperature characteristics was clarified based on the analyses of eight typical iron ores. The results indicate that high-temperature characteristics of iron ores in various alumina types are different. Higher Al2O3 concentration is deleterious to assimilability and liquid phase fluidity, but the influence extent of each alumina type is substantially different. Kaolinite (Al2O3·2SiO2·2H2O) contributes to correspondingly better assimilability, followed by hercynite (Fe(Fe, Al)2O4), gibbsite (Al(OH)3), diaspore (AlO(OH)), and free state alumina (Al2O3) in turn. Diaspore promotes relatively higher liquid phase fluidity, followed by kaolinite, free state alumina, and hercynite, while gibbsite possesses the maximum adverse impact. Kaolinite and hercynite are more beneficial to form dendritic or acicular silico-ferrite of calcium and alumina (SFCA) with high strength due to the better reactivity, and gibbsite and diaspore lead to more formation of relatively lower strength lamellar or tabular SFCA, while free state alumina is preferable to form disseminated SCFA with rather poorer strength. Kaolinite and hercynite are the most desirable alumina types for sintering rather than free state alumina.

Limonitic laterite contains low iron and nickel grades and much high smelting minerals and loss on ignition (LOI), identified as refractory iron ore for sintering. Thus, sinter pot tests of limonitic laterite via pressurized densification sintering and its intensification mechanism were conducted, and the industrial application prospect was explored. The results indicate that the sintering performance of the limonitic laterite of the new process is significantly improved with the tumble index and productivity increased by 19.2% and 18.6%, respectively, and solid fuel rate lowered by 10.3%. The external pressure field promotes the synchronization of heat front velocity and combustion front velocity for better sintering heat and mass transfer conditions, which also greatly improves the mineral compositions and microstructure of the product sinter. The microstructure is converted from large thin-wall pores into small thin-wall or large thick-wall pores with the sinter porosity decreased by 42.4%. Much close interlocking texture between hercynite and silico-ferrite of calcium and alumina (SFCA) is formed with hercynite grains aggregation and growth, and SFCA amount substantially increased. The better sintering performance will bring about a remarkable economic benefit of 282.78 million RMB/a if the industrial application is implemented. The pressurized densification sintering process is considered as one of the effective technologies for improving limonitic laterite sintering.

In this study, a novel process was established for extraction of Fe and Al from a complex high aluminum iron ore (33.43% Fetotal and 19.09% Al2O3). The main steps in the proposed process included pre-reducing high alumina iron ore and subsequent smelting to produce pig iron and rich-alumina slag, followed by alkaline leaching of the slag to obtain sodium aluminate solution and a clean slag. When smelting the pre-reduced high alumina iron ore pellets at 1625 °C for 30 min with a slag basicity of 0.40, the pig iron yielded 97.08% Fe and extracted 0.13% Al2O3, together with an iron recovery of 94.54%. In addition, more than 68.93% Al2O3 was recovered by leaching the slag, which was achieved by firstly roasted the slag at 900 °C for 2 h and then alkaline leaching at 95 °C for 2 h with a liquid-to-solid ratio of 10 mL/g. In addition, the alkaline leaching slag could potentially be used as raw material for construction purpose, which mainly consisted of SiO2 and CaO.

Generally, the Cu-bearing direct reduction iron powder (CBDRI) obtained from a direct reduction-magnetic separation process of waste copper slag contains a high content of impurities and cannot be directly used to produce Cu-bearing special steel. In this paper, further smelting treatment of CBDRI was conducted to remove its impurities (such as S, SiO2, Al2O3, CaO and MgO) and acquire a high-quality Fe−Cu master alloy. The results show that the Fe−Cu master alloy, assaying 95.9% Fe, 1.4% Cu and minor impurities, can be obtained from the smelting process at 1550 °C for 40 min with 1.0 basicity. Meanwhile, the corresponding iron and copper recoveries are 98.6% and 97.2%, respectively. Theoretical calculations and experimental results show that appropriate basicity (0.9~1.1) is beneficial for the recovery of Fe and Cu from a thermodynamic viewpoint due to the excellent fluidity of the slag in this basicity range. Moreover, the mechanism of desulfurization was revealed by calculating the sulfide capacity and the desulfurization reaction kinetics. Increasing the binary basicity of the slag benefits both the sulfide capacity and diffusion coefficient of the sulfur in the molten slag, resulting in higher desulfurization efficiency and lower S content in the master alloy.

The reduction roasting ammonia leaching process (RRAL) originally defined by Caron (1950) has been extensively applied to treat low grade nickel laterite and a large amount of slag-containing some valuable metals, has been generated and accumulated over the years since then. However, there are no reports on how to utilize it based on its essential properties. In this investigation, the textural and mineralogical characterization of the typical nickel slag from RRAL in Western Australia was performed by X-ray diffraction (XRD), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The results show that the nickel slag is dominated by magnetite, maghemite, gangue minerals and minor Cr-spinel. The magnetite and maghemite possess simple distribution relationship with other minerals and their particles are highly variable with most over 50 μm, which are easily able to be recovered. In term of the complex association and distribution feature of chromium and nickel minerals, it is very difficult to recovery them. Meanwhile, an economically viable extraction process was proposed to preliminarily utilize the nickel slag based on textural and mineralogical characteristics of the slag, and the magnetic concentrate, assaying about 62% iron grade at over 75% recovery rate, was obtained through the recommended method.

In this paper, an effective method was developed to remove phosphorus and upgrade iron from high phosphorus oolitic hematite ore by high temperature flash reduction—a wet magnetic separation process. A thermodynamic analysis of iron and phosphorus mineral reactions and experiments with Fe-P separation process were performed, and the mechanism of phosphorus removal and beneficiation of iron is discussed as well. The results show that under the proper conditions, a final metallic iron powder assaying over 91% Fe and 0.25% P was obtained with iron recovery of 90% and phosphorus removal rate of 91.79% using the new process, indicating that the high temperature flash reduction process is a feasible and efficient way to process this kind of complex and refractory iron ore. Moreover, sodium sulfate is found to be capable of improving the removal of phosphorus and the upgrading of iron, as well as enhancing the growth of metallic iron grains significantly for higher recovery of iron.

In the paper, a new technology was developed to improve the beneficiation of copper and iron components from copper slag, by modifying the molten slag to promote the mineralization of valuable minerals and to induce the growth of mineral grains. Various parameters, including binary basicity, dosage of compound additive, modification temperature, cooling rate and the end point temperature of slow cooling were investigated. Meanwhile, optical microscope, scanning electron microscope and energy dispersive spectrometer (SEM-EDS) was employed to determine the mineralogy of the modified and unmodified slag, as well as to reveal the mechanisms of enhancing beneficiation. The results show that under the proper conditions, the copper grade of rougher copper concentrate was increased from 6.43% to 11.04%, iron recovery of magnetic separation was increased significantly from 32.40% to 63.26%, and other evaluation indexes were changed slightly, in comparison with unmodified copper slag. Moreover, matte and magnetite grains in the modified slag aggregated together and grew obviously to the mean size of over 50 μm, resulting in an improvement of beneficiation of copper and iron.